1. Field of the Invention
The invention relates to a turbomachine, in particular a compressor of a gas turbine.
2. Discussion of Background
In turbomachines with high thermal loading, in particular in the case of compressor stages of modern gas turbines, the rotor shaft is to be regarded as a particularly endangered component. As a consequence of the extreme temperature loadings, the life of conventionally used materials falls drastically so that additional measures have to be taken in order to deal with this problem.
A first approach to a solution consists in providing so-called heat shields which prevent direct contact between the heated flow medium and the rotor shaft and, by this means, should keep the heating within limits considered to be permissible. A disadvantageous feature is then the increase in the manufacturing costs and complexity of the turbomachine due to the additional components.
A further approach to a solution consists in manufacturing the rotor shaft from a material with improved high temperature behavior. Although such materials are available, problems arise in practical use due to a differing thermal expansion behavior as compared with the materials of adjacent components, in addition to increased material costs. Transient procedures in particular, such as, for example, the starting of the machine, introduce enormous difficulties due to the different time-dependent thermal expansion behavior.
Finally, it is also known to cool rotor shafts, made from conventional materials, by means of a central coolant hole which passes through the rotor shaft. Such a solution, however, is extremely cost-intensive and, in addition, not very effective.